Adjustable mixing device

ABSTRACT

An adjustable mixing device for mixing and blending fluids in a container which has a fluid impeller adapted for pumping the fluids substantially laterally in counter-rotating and circular continuous motion in the container that is area-adjustable for varying the volume of fluids pumped to adjust the torque load on the impeller to prevent overload on the mixing motor during start-up. The impeller of the mixing device can be adjusted from outside the container without impeller removal.

United States Patent Davis, Jr. Nov. 18, 1975 ADJUSTABLE MIXING DEVICE 3,414,245 12/1968 Frazer .1 259/96 [76] Inventor: Philip E. Davis, Jr., PO. Box

35729 Houston, 77035 Primary Examiner-Robert W. Jenkins t Filed: J 1974 Attorney, Agent or Firm Pravel & ilson [21] App]. No.: 479,116 [57] ABSTRACT An adjustable mixing device for mixin and blending 25938661232??? fluids in a container which has a fluid impeller [58] id 8 23 24 adapted for pumping the fluids substantially laterally e 0 67 6 i in counter-rotating and circular continuous motion in I the container that is area-adjustable for varying the References Cited volume of fluids pumped to ad ust the torque load on the impeller to prevent overload on the mixing motor UNITED STATES PATENTS" during start-up. The impeller of the mixing device can 2,619,330 11/1952 Willems 259/96 be adjusted from outside the container without impel- 2,738,174 3/1956 Magnant.... ler removal. 3,326,532 6/1967 Lodge 3,339,897 9/1967 Davis 259/8 11 Claims, 3 Drawing Figures L- hail c f5? US. Patent Nov. 18, 1975 Him...

I'HHIII- ADJUSTABLE MIXING DEVICE BACKGROUND OF THE INVENTION The present invention relates to mixing devices and more particularly pertains to apparatus for mixing and blending highly viscous fluids such as drilling fluids, concrete, petroleum crudes, aqueous oleaginous emulsions and the like.

Many viscous fluids, prepared by mixing or blending liquid and dry granular ingredients, substantially immiscible liquids and the like have tendencies to change viscosities and/or to separate into layers upon standing. For example, drilling fluids prepared from intimately mixed dry materials and liquids, gels and other special ingredients, tend to settle out or precipitate upon standing into thin liquid upper layers and heavy bottom residues or, in some instances, to form thixotropic gels. This occurs frequently at oil and gas well drilling sites due to constant interruptions in the drilling operation. Another example is petroleum crudes which have the tendency to form substantially undefined layers of differing viscosities during storage.

The separation and viscosity change properties of these highly viscous fluids create problems for conventional mixing devices employed to remix these fluids to consistent viscosities throughout. Due to these properties, large starting torques are required to restart agitation of the fluids. Such large starting torques place increased stress on the mixing device employed which can result in frequent breakdown and repair problems. For example, the required large starting torques can result in overloading the mixing device power source, thereby causing damage thereto. Moreover, increased energy is required to produce the large starting torques required which may be unavailable or in reduced supply in remote operating areas, such as the abovementioned remote drilling sites.

DESCRIPTION OF THE PRIOR ART US. Pat. No. 3,339,897 issued to the present inventor on Sept. 5, I967, discloses a continuous mixing device for drilling fluids which has a turbine-type impeller mounted with a driving shaft that is rotated by a power source. The mixing device is believed to be a substantial advance in the art of mixing devices useful for mixing and remixing viscous fluids. However, it has been found that the described mixing device can be overloaded during starting or opertating under heavy torque loads caused by highly viscous or dense fluids. The present invention is an improvement of the device described in the aforesaid US. Pat. No. 3,339,897.

SUMMARY OF THE INVENTION The present invention is an improved mixing device for agitating fluids in a container that includes a mixing motor mounted with a drive shaft that extends into the fluid with an area-adjustable impeller mounted thereon. The area-adjustable impeller is adapted for positively displacing or pumping the fluid in the container outwardly substantially laterally from the drive shaft to provide counter-rotating and circular currents in the fluid throughout the container. The area-adjustable impeller is adapted for adjustment to vary the vol ume of fluid positively displaced during rotation so as to control the torque load on the motor during start-up and operation. The impeller is adjustable from the exterior of the container without removal of the impeller or mixing device from the container.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partially schematic and partially in section, of the mixing device of this invention with the improved area-adjustable impeller in partial cross-section;

FIG. 2 is a cross-sectional view of the area-adjustable impeller taken along line 2-2 of FIG. 1 which illustrates in detail the impeller blades of the invention; and

FIG. 3 is a fragmentary view, partially in cross-section, which illustrates certain details of the area-adjustable impeller of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, the improved mixing apparatus of the invention, generally M, is adapted for mounting with a container, generally C, which is preferably a large cylindrical structure of large capacity including a cyclindrical wall 10 having an annular flange 10a attached to its upper edge, a bottom 10b and a circular roof 10c detachably mounted with the annular flange 10a. Container C is provided with an inlet means 12 for admitting fluids to be mixed into the container C and an outlet means 14 which includes a valve 14a to control the fluid flow from the container C.

The circular roof 10c is provided with an opening 10d that is located substantially in its center and the mixing apparatus M is mounted with the roof 10c in vertical alignment with opening 10d. The mixing apparatus M includes a shaft means S extending vertically through the opening 10d into the container C and an impeller means I mounted at the lower end of the drive shaft means S and disposed within the container C for immersion in and agitation of a fluid in the container. The drive shaft means S extends through a support means X which is provided for supporting the drive shaft means S and impeller means I vertically within the container C for axial rotation. The support means X is attached to roof 10c about the roof opening 10d by any conventional means, such as bolts, 10:2.

The mixing apparatus M further includes driving means D mounted with the upper end of the drive shaft means S for imparting a driving force for axially rotating the drive shaft means S and the impeller means I, and an area-adjusting means A for adjusting the surface area of the impeller means I coacting with the fluid during axial rotation for controlling the torque required from the driving means D to provide the axial rotation.

As shown in FIG. 1, the drive shaft means S includes upper and lower hollow drive shaft members 20a and 20b attached in vertical axial alignment by means of rigid coupling members 21a and 21b which are disposed substantially immediately below roof within the container C. Upper hollow shaft member 20a is mounted at substantially its upper end with the driving means D and extends through and is supportably mounted with the support means X. The lower shaft member 20b has mounted at its lower end the impeller means I which is located above the bottom 10b of the container C. Preferably, the rigid coupling members 21a and 21b are bolted together (not shown) so as to provide easy removal of the lower drive shaft member 20b and the impeller means I for cleaning, repair, storage, transfer and the like.

The upper hollow drive shaft member 20a extends vertically through the roof opening d and through the support means X which includes a support housing 30 mounted with the roof 10c and a plurality of bearing means 31a and 31b mounted therewith and rotatably mounted with the upper shaft a. The bearing means 31a, 31b are preferably located at the upper and lower ends of the support housing and support the upper drive shaft means S and impeller means I for axial rotation.

The upper hollow drive shaft member 20a also is mounted at substantially its upper end with a speed control means R of the drive means D. The speed control means R can be any conventional type known in the art for varying the axial rotation speed and drive force of the drive shaft means S and the impeller means I under varying torque load conditions and is preferably a conventional gear reduction box 40, as shown in FIG. 1 partially in phantom. As known, such a gear reduction box has a plurality of driven gears 40a adapted for attachment with the upper drive shaft 20a and an equal plurality of driving gears 40b mounted with a driving gear shaft 400 which is further attached at its upper end with a driven pulley 40d. The driven gears 40a and the driving gears 40b are adapted for engagement to provide predetermined ratios between the speed of rotation of the drive shaft means S and the speed provided at the driven pulley 40d. Speed and driving force is provided at the driven pulley 40d by motor means such as an electric motor having a driving pulley 50a at one end connected by a belt drive 50b to the driven pulley-40b of the gear reduction box 40.

The gear reduction box 40 includes a gear housing 40c which can be supported by attachment to the support housing 30 (not shown) if desirable. The electric motor 50 can be supported bymounting with the support housing 30 such as by means of a stanchion 50c.

The impeller means I of the mixing apparatus M is of turbine-type construction including a plurality of areaadjustable impeller blade means, generally B, extending outwardly substantially laterally from the axial alignment of the impeller means I and the drive shaft means S for positively displacing a portion of the fluid in the container C outwardly and laterally in counterrotating' and circular turbulences or currents to accomplish the desired fluid mixing. The impeller blade means B are area-adjustable and coact with the fluid for varying the volume of fluid positively displaced during rotation so as to reduce the torque load required to axially rotate the impeller means I. More particularly, the impeller means I is illustrated in FIG. 1 as including an upper impeller 60 mounted with a driving hub 61 which is in turn mounted with the lower end of the hollow drive shaft member 20b and extends axially therewith. The upper impeller 60 includes a plurality of arcuate-shaped driving blades 62 attached at their respective inward tips 62a to the driving hub 61 that extend outwardly substantially laterally to the axis of the hub 61. The driving blades 62 are disposed so as to provide vertical longitudinal fluid displacement surfaces relative to the vertical axis of driving hub 61 and drive shaft means S. An upper circular plate 63 is transversely attached to the upper edges of the driving blades 62 and has an axial opening 64 about the driving hub 61 which defines an axial intake means 64a for drawing a portion of the fluid to the impeller blade means B for positive outward displacement as more particularly described hereafter. The upper circular plate 63 has a radius substantially equal to the distance the arcuate driving blades 62 extend laterally from the driving hub 61. I

The impeller means I further includes a lower impeller mounted with a driven hub 71 which is in axial alignment with driving hub 61 and is supportably mounted with the area-adjusting means A. The lower impeller 70 is adapted for axial rotation and for upward and downward longitudinal movement relative to the upper impeller 60. The lower impeller 70 also includes a plurality of arcuate-shaped driven blades 72 attached at their respective inward tips 72a to the driven hub 71 and extend outwardly substantially laterally therefrom. Driven blades 72 are parallel relative to driving blades 62 and are thus disposed to provide vertical longitudinal fluid displacement surfaces relative to the axis of the drive shaft means S and impeller means I. A lower circular plate 73 is transversely attached to the lower edges of the driven blades 72 that is parallel to the upper circular plate 63 to provide a space therebetween through which the portion of fluid is outwardly positively displaced. Lower circular plate 73 has a radius substantially equal to the distance driven blades 72 extend laterally from driven hub 71 and has an axial opening 74 which defines an axial intake means 74a for drawing a portion of the fluid inwardly for positive outward displacement.

Upper impeller 60 and lower impeller 70 are positioned relative to each other so that the lower edges 62b of driving blades 62 and the upper edges 72b of r driven blades 72 overlap to provide an interference fit. In operation, the rotational driving force provided by driving means D through drive shaft means S to the upper impeller 60 is imparted by driving blades 62 to the driven blades 72 so as to cause the upper impeller 60 to drive the lower impeller 70. The interference fit of driving blades 62 and driven blades 72 also provide longitudinal areas between upper circular plate 64 and lower circular plate 74 which coact with the portion of the fluid to positively displace it outwardly from the im peller means I axis. r

Referring now to FIG. 2, which is a cross-sectional view of the impeller means I taken along line 22 of.

FIG. 1, the plurality of impeller blades 62 are spaced Referring again to FIG. 1, the lower impeller 70 and driven hub 71 are supported relative to the upper impeller 60 and driving hub 61 for upward and downward longitudinal movement by the area-adjusting means A which includes an adjusting rod adaptable for supportable mounting at its lower end with the driven hub 71 and extending axially within the hollow drive shaft means S and through the speed control means R. The adjustment rod 80 is freely rotatable relative to the hollow drive shaft means S. The lower end of adjustment rod 80 is threadably mounted with a support nut 81 upon which the driven hub 71 rests. The upper end of adjustment rod 80 is threadably attached to an adjustment nut 82 which has a hand wheel 83 attached thereto. The adjustment nut 82 engages at its lower end the upper end c of the upper hollow shaft member 20a and is supported thereon. Axial rotation of adjustment nut 82 raises or lowers the adjustment rod 80 longitudinally which in turn raises or lowers the lower impeller 70. This raising and lowering of lower impeller 70 accordingly increases and decreases the total longitudinal area of impeller blades 62 and 72 which coacts with the fluid so as to vary the volume of fluid positively displaced outwardly during rotation of the impeller means I.

Referring now to FIG. 3, the cylindrical driving hub 61 is illustrated as having an axial bore 61a through which the lower end of the hollow drive shaft member 20b extends. The hollow shaft member 20b and the hub 61 have respective grooves 20d and 61b aligned with each other so as to receive a key K which locks them together. A circular anticavitation plate 90 is attached by an annular weld 90a to the upper end of the cylindrical driving hub 61 parallel to the upper and lower circular plates 63 and 72. As shown in FIG. 1, the circular anticavitation plate 90 is spaced above the axial intake means 642. In operation, the anticavitation plate 90 prevents vortexing of the fluid and thereby prevents the entrance of air into the intake means 64a.

Referring now to FIG. 3, the driving hub 61 is shown as also having an axial bore 61c at its lower end that is adapted to receive the driving hub 71 for upward and downward longitudinal movement therein. Cylindrical driven hub 71 has a diameter slightly less than the axial bore 61c and is disposed therein. Driven hub 71 also has an axial bore 71a slightly in excess of the diameter of adjustment rod 80. Adjustment rod 80, extending axially through hollow drive shaft means S and being free to rotate relative thereto, such as during longitudinal adjustment, also extends through the bore 71a of the driven shaft 71. The adjustment rod 80 and the hub 71 have respective grooves 80a and 71b in alignment and adapted to receive a key Y which locks them together. The support nut 81 threadably attached to the lower end of adjustment rod 80 supports the driven hub 71 within the axial bore 61c of the driving hub 61.

The driving blades 62 of the upper impeller 60 are attached by welding, bolting or like attachment of their upward portions of their inward tips 62a to the lower end of the driving hub 61 so that the lower edges 62b extend below and beyond the driving hub 61 lower end. The driven blades 72 of the lower impeller 70 are likewise attached to the lower end of the driven hub 71 at their inward tips 72a. However, the driven blades 72 have notches 72d at the upper portions of their respective inward tips 72a which are adapted to receive the lower end of driving hub 61 when the driven hub 71 is longitudinally raised in the driving hub axial bore 61c. The driving blade lower edges 62b and the driven blade upper edges 72b are adapted to overlap in an interference flt while the driven hub 71 is disposed within the driving hub bore 61c so as to impart the rotational driving force to the lower impeller 70 as mentioned hereinbefore.

As shown in FIG. 3, each of the impeller blades 62 and 72 have respective curved leading edges 62d and 72e adjacent the respective axial openings 64 and 74 of the respective parallel circular plates 63 and 73. These curved edges 62d and 72ebite portions of the fluid in the container C during rotation so as to draw portions of the fluid into the impeller means I for outward displacement during rotation.

In operation, the mixing apparatus M of this invention can be employed to intimately mix and agitate substantially any type of viscous fluid, to blend wet and dry ingredients, or to blend fluids capable of changing viscosity without the heretofore attendant dangers of motor damage due to excessive torque loads. Since torque loads and power requirements are usually the heaviest during start-up of the mixing device M when the impeller means I is immersed in a fluid in the container C, this description of operation will begin therewith. Prior to initial start-up, it is preferred to adjust the total longitudinal area provided by the blade means B which coact with the fluid for positive displacement thereof. This is accomplished by rotating the adjustment nut 82 in the proper direction to raise or lower the adjustment rod which in turn longitudinally raises or lowers the lower impeller 70, thereby decreasing or increasing the total longitudinal area of the blade means B to that desired. The volume of fluid which can be positively displaced outwardly during initial rotation is thus varied to the desired amount which will result in a reduced torque load required for rotation.

When power is supplied to the motor 50, a driving force is imparted toithe gear reduction box 40 which rotates the drive shaft means S and the upper impeller 70. The rotational driving force is imparted through the interference fit of the driving blades 62 and the driven impeller blades 72 to rotate the lower impeller 70. During rotation, a portion of the fluid is drawn through the intake means 64a and 74a and positively displaced outwardly substantially laterally by the blades 62 and 72 coacting with the parallel upper and lower plates 63 and 73. Continuous rotation of the impeller means I causes continuous circular and counterrotating turbulences of the fluid within the container as shown by arrows T in FIG. 1 whereby substantially all the fluid in the container C is intimately mixed. The anticavitation plate prevents vortexing of the fluid, which thereby prevents excessive air bubbles during mixing. The anticavitation plate, accordingly, maintains the fluid in a substantially level position.

In the event it is determined that the torque load required for rotation of the impeller means I in the particular fluid to be mixed is too great, or in the alternative it is less than that which the motor 50 can handle without damage, the adjustment nut 82 can be rotated in the proper direction so* as to increase or decrease the total longitudinal area of the blade means B coacting with the fluid as described hereinbefore. Thus, it can be readily appreciated that the adjustment can be made as desired to control the torque load required for rotation.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

I claim:

1. A mixing apparatus for agitating fluids in a container comprising:

a. drive shaft means adapted to extend into a container,

b. support means for supporting said drive shaft means for axial rotation;

c. driving means mounted with one end of said drive shaft means for imparting a driving force thereto for axial rotation;

d. impeller means mounted with an opposite end of said drive shaft means for immersion in a fluid in a container having a surface coacting with the fluid for positively displacing a portion of said fluid outward substantially laterally from the axial alignment of said drive shaft means and into counterrotating and circulating turbulences within said container; and

e. area-adjusting means for adjusting the surface area of said impeller means coacting with the fluid for varying the volume of fluid positively displaced during axial rotation for controlling the torque required from said driving means;

f. said impeller means comprising 1. a first impeller member having at least one blade member mounted therewith;

2. a second impeller member having at least one blade member mounted therewith;

3. said second impeller member being disposed in longitudinal spaced relationship with said first impeller member to provide an adjustable space therebetween and to provide a longitudinal overlapping arrangement of said blade members for engagement of said blade members to form an adjustable surface for said coacting with a portion of the fluid;

4. one of said impeller members mounted with said drive shaft for fixed axial rotation;

5. one of said impeller members rotatably mounted with said area-adjusting means for axial rotation and adapted for longitudinal movement relative to said other impeller member whereby the fixedly mounted impeller member drives the rotatably mounted impeller member during axial rotation; and

6. at least one of said impeller members having an axial opening to provide for fluid flow in the container into the space between said impeller members for positive displacement thereof substantially laterally through said space by said longitudinally overlapping blade members during axial rotation.

2. The mixing apparatus of claim 1, including:

means mounting said area-adjusting means for adjusting said impeller meear'is from the exterior of the container.

3. The mixing apparatus of claim 1, including:

anticavitation means adapted for mounting with said impeller means for maintaining said fluid in the container substantially level during said axial rotation.

4. The mixing apparatus of claim 1, wherein said driving means includes: g

a. speed control means mounted with said drive shaft means, and

b. motor means connected therewith for imparting a driving force and rotation to said speed control means and drive shaft means.

5. The mixing apparatus of claim 1 wherein:

a. said first impeller member includes a first hub member mounted with said drive shaft means and disposed in axial alignment relative thereto, :said first hub member having at least one blade member mounted therewith; and

b. said second impeller member includes a second hub member rotatably mounted with said areaadjusting means and disposed in axial alignment relative to said drive shaft means and longitudinally movable relative to said first hub member upon actuation of said adjusting means, said second hub member having at least one blade member mounted therewith.

6. The apparatus of claim 5 wherein said adjusting means includes:

a. an adjustment rod having one end adapted for mounting with said second impeller hub member and having an opposite end extending exteriorly of said container, the longitudinal axis of said adjustment rod being in substantial alignment with the longitudinal axis of said drive shaft means; and

b; means mounted with said opposite end of said adjustment rod for adjusting said adjustment rod upwardly and downwardly about its longitudinal axis whereby said second impeller member is also adjusted upwardly and downwardly relative to said first impeller member to provide an increase or decrease in the total longitudinal area of said blade members which coact with the fluid positively displaced through the space between said impeller members.

7. The mixing apparatus of claim 6 wherein said means for adjusting the adjustment rod includes:

anactuating member threadably' mounted with said opposite end of said adjustment rod and rotatable for axial adjustment of said adjustment rod.

8. The mixing apparatus of claim 1 including:

a; an upper circular plate attached to the upper edge of said blade member of said first impeller member;

; and

b. a lower circular plate attached to the bottom edge of saidblade member of said second impeller member and parallel to said upper circular plate;

said blade members being longitudinally adjustable relative to each other for positioning the lower edge of the first impeller blade member and the upper edge of the second impeller blade member so as to overlap each other in variable amounts upon adjustment thereof by said adjusting means to transmit a driving force from one of said impeller blade members to said other impeller blade member during said axial rotation; and

at least one of said circular plates having said axial b. said second impeller member including a second i hub member rotatably mounted with said areaadjusting means and disposed in axial alignment.

relative to said drive shaft means and longitudinally movable relative to saidfirst hub member upon actuation of said adjusting means, said second hub member having said second impeller blade member mounted therewith.

10. The mixingapparatu s of claim 9 wherein said blade members of 'ea'ch'of said impeller members are respectively mounted with said first and second hub members, each of said blade members having a sub- 9 10 stantially arcuate shape and extending substantially latsaid first impeller member includes a plurality of erally from the respective axial alignments of each of blade members; and said hub members to the respective peripheries of said said second impeller member includes a plurality of upper and lower circular plates. blade members.

11. The mixing apparatus of claim 8 wherein: 

1. A mixing apparatus for agitating fluids in a container comprising: a. drive shaft means adapted to extend into a container, b. support means for supporting said drive shaft means for axial rotation; c. driving means mounted with one end of said drive shaft means for imparting a driving force thereto for axial rotation; d. impeller means mounted with an opposite end of said drive shaft means for immersion in a fluid in a container having a surface coacting with the fluid for positively displacing a portion of said fluid outward substantially laterally from the axial alignment of said drive shaft means and into counterrotating and circulating turbulences within said container; and e. area-adjusting means for adjusting the surface area of said impeller means coacting with the fluid for varying the volume of fluid positively displaced during axial rotation for controlling the torque required from said driving means; f. said impeller means comprising
 1. a first impeller member having at least one blade member mounted therewith;
 2. a second impeller member having at least one blade member mounted therewith;
 3. said second impeller member being disposed in longitudinal spaced relationship with said first impeller member to provide an adjustable space therebetween and to provide a longitudinal overlapping arrangement of said blade members for engagement of said blade members to form an adjustable surface for said coacting with a portion of the fluid;
 4. one of said impeller members mounted with said drive shaft for fixed axial rotation;
 5. one of said impeller members rotatably mounted with said area-adjusting means for axial rotation and adapted for longitudinal movement relative to said other impeller member whereby the fixedly mounted impeller member drives the rotatably mounted impeller member during axial rotation; and
 6. at least one of said impeller members having an axial opening to provide for fluid Flow in the container into the space between said impeller members for positive displacement thereof substantially laterally through said space by said longitudinally overlapping blade members during axial rotation.
 2. a second impeller member having at least one blade member mounted therewith;
 2. The mixing apparatus of claim 1, including: means mounting said area-adjusting means for adjusting said impeller meeans from the exterior of the container.
 3. The mixing apparatus of claim 1, including: anticavitation means adapted for mounting with said impeller means for maintaining said fluid in the container substantially level during said axial rotation.
 3. said second impeller member being disposed in longitudinal spaced relationship with said first impeller member to provide an adjustable space therebetween and to provide a longitudinal overlapping arrangement of said blade members for engagement of said blade members to form an adjustable surface for said coacting with a portion of the fluid;
 4. one of said impeller members mounted with said drive shaft for fixed axial rotation;
 4. The mixing apparatus of claim 1, wherein said driving means includes: a. speed control means mounted with said drive shaft means, and b. motor means connected therewith for imparting a driving force and rotation to said speed control means and drive shaft means.
 5. The mixing apparatus of claim 1 wherein: a. said first impeller member includes a first hub member mounted with said drive shaft means and disposed in axial alignment relative thereto, said first hub member having at least one blade member mounted therewith; and b. said second impeller member includes a second hub member rotatably mounted with said area-adjusting means and disposed in axial alignment relative to said drive shaft means and longitudinally movable relative to said first hub member upon actuation of said adjusting means, said second hub member having at least one blade member mounted therewith.
 5. one of said impeller members rotatably mounted with said area-adjusting means for axial rotation and adapted for longitudinal movement relative to said other impeller member whereby the fixedly mounted impeller member drives the rotatably mounted impeller member during axial rotation; and
 6. at least one of said impeller members having an axial opening to provide for fluid Flow in the container into the space between said impeller members for positive displacement thereof substantially laterally through said space by said longitudinally overlapping blade members during axial rotation.
 6. The apparatus of claim 5 wherein said adjusting means includes: a. an adjustment rod having one end adapted for mounting with said second impeller hub member and having an opposite end extending exteriorly of said container, the longitudinal axis of said adjustment rod being in substantial alignment with the longitudinal axis of said drive shaft means; and b. means mounted with said opposite end of said adjustment rod for adjusting said adjustment rod upwardly and downwardly about its longitudinal axis whereby said second impeller member is also adjusted upwardly and downwardly relative to said first impeller member to provide an increase or decrease in the total longitudinal area of said blade members which coact with the fluid positively displaced through the space between said impeller members.
 7. The mixing apparatus of claim 6 wherein said means for adjusting the adjustment rod includes: an actuating member threadably mounted with said opposite end of said adjustment rod and rotatable for axial adjustment of said adjustment rod.
 8. The mixing apparatus of claim 1 including: a. an upper circular plate attached to the upper edge of said blade member of said first impeller member; and b. a lower circular plate attached to the bottom edge of said blade member of said second impeller member and parallel to said upper circular plate; said blade members being longitudinally adjustable relative to each other for positioning the lower edge of the first impeller blade member and the upper edge of the second impeller blade member so as to overlap each other in variable amounts upon adjustment thereof by said adjusting means to transmit a driving force from one of said impeller blade members to said other impeller blade member during said axial rotation; and at least one of said circular plates having said axial opening to provide for said fluid flow into said space between said impeller members.
 9. The mixing apparatus of claim 8 wherein: a. said first impeller member includes a first hub member mounted with said drive shaft means and disposed in axial alignment relative thereto, said first hub member having said blade member mounted therewith; and b. said second impeller member including a second hub member rotatably mounted with said area-adjusting means and disposed in axial alignment relative to said drive shaft means and longitudinally movable relative to said first hub member upon actuation of said adjusting means, said second hub member Having said second impeller blade member mounted therewith.
 10. The mixing apparatus of claim 9 wherein said blade members of each of said impeller members are respectively mounted with said first and second hub members, each of said blade members having a substantially arcuate shape and extending substantially laterally from the respective axial alignments of each of said hub members to the respective peripheries of said upper and lower circular plates.
 11. The mixing apparatus of claim 8 wherein: said first impeller member includes a plurality of blade members; and said second impeller member includes a plurality of blade members. 